Backup appliances that provide continuous data protection for a clustered application may need to know when a cluster node loses connectivity to the backup appliance. Disconnection of a cluster node may result in some Input and/or Output (“I/O”) on the node not being protected, and detection of this missed I/O condition (i.e., blackout) may be critical for correct functioning of the backup appliance. Traditional solutions may address this problem by maintaining the state of connectivity of each node in the cluster at some cluster-wide central location. The central location could be a cluster-accessible storage device (e.g., a file or a block on shared storage device). The backup appliance may detect the connectivity state of each cluster node by periodically reading from the central storage device.
Unfortunately, provisioning a cluster-wide accessible storage device is problematic for a variety of reasons. For example, if the central location is a data store owned by the cluster monitor, the backup appliance may have a problem reading the data store since the data store may be cluster monitor proprietary and interfaces to read the data store may be highly specific to the particular cluster monitor.
Another challenge associated with provisioning cluster-wide accessible storage is that new storage resources (e.g., spindles, ports, mapping entries, etc.) may need to be allocated by a network administrator when the network administrator is adding the backup appliance to an already-configured application cluster. Furthermore, the extra storage resource allocated by the network administrator may need to comply with one or more of a variety of constraints: 1) the storage resource should be connected to all cluster nodes; 2) the storage resource should originate from the same storage controller as the production storage; 3) the storage resource needs to be configured for a specific transport; 4) the storage resource needs to support a specific filesystem; and/or 5) the storage resource needs to be a specified minimum size. Complying with one or more of these constraints to provide a storage device for maintaining connectivity information may be cumbersome and problematic. What is needed, therefore, is a more efficient and effective mechanism for managing connectivity information of cluster nodes.